The present invention relates to a method for observing defects and its apparatus having a function of detecting defects and the like existing on a sample surface, or sample surface or around the sample surface.
For example, in a semiconductor device manufacturing process, when a pattern defect (hereinbelow, described as a defect but it includes on foreign material and a pattern defect) such as foreign material, a short circuit or wire break exists on a semiconductor substrate (wafer), it becomes the failure factor of insulation failure, short circuit and the like. Further, in accordance with microminiaturization of circuit pattern formed on a wafer, finer defects may be the cause of capacitor insulation failure, breakage of gate oxide film or the like. Among these defects, the foreign material may be caused in various statuses, e.g., caused from a movable part of a transfer device, caused from a human body, react-generated with process gas inside a processing device, or may be mixed in chemicals and materials. Further, the pattern defect such as short circuit or wire break is caused due to variation of process conditions, variation of the processing device or the like. Accordingly, it is important for mass-production of semiconductor device to detect defects caused in the manufacturing process, quickly find the source of outbreaks of the defects and stop manufacture of defective products.
Conventionally, as a method of thorough inquiry into the factor of occurrence of defects, there has been a method of first specifying a defect position with a defect inspecting apparatus, then observing and classifying the defects in detail with a SEM (Scanning Electron Microscope) or the like, and performing a comparison with a database, to estimate the factor of occurrence of the defects.
Note that the defect inspecting apparatus is an optical defect inspecting apparatus to irradiate the surface of a semiconductor substrate with laser, and perform dark field observation on scattered light from a defect, to specify the position of the defect, an optical appearance inspecting apparatus to irradiate with a lamp or laser, or an electron beam, to detect a bright field optical image of the semiconductor substrate, and by comparing this with reference information, specify a defect position on the semiconductor substrate, or a SEM inspecting apparatus. Regarding such observing method, there is disclosure in Japanese Published Unexamined Patent Application No. Hei 7-270144 (Patent Literature 1) and or Japanese Published Unexamined Patent Application No. 2000-352697 (Patent Literature 2).
Further, regarding an apparatus to observe a defect with a SEM, U.S. Pat. No. 6,407,373 (Patent Literature 3), Japanese Published Unexamined Patent Application No. 2007-71803 (Patent Literature 4) and Japanese Published Unexamined Patent Application No. 2007-235023 (Patent Literature 5) respectively disclose a method and its apparatus for detecting a position on a sample with an optical microscope attached to a SEM defect inspecting apparatus using positional information defect on the sample detected with the other inspecting apparatus, correcting the defect positional information obtained by detection with other inspecting apparatus, and observing (reviewing) the defect in detail with the SEM defect inspecting apparatus, and, upon observation of defect with a SEM defect inspecting apparatus, optically detecting the height of the sample surface and adjusting the sample surface to a focus position of the SEM.